Adjustable scaffold clamp



7 Oct; 2Q, 1953 P. GRAY v 2, ,223

ADJUSTABLE YSCAFFCLD CLAMP v Filed Dec; 14. 1948 3 Sheets-Sheet;

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INVENTOR. PERCK GRAY BY g Z Oct. 20, 1953 GRAY ADJUSTABLE SCAFFOLD CLAMP 5 Sheets-Shet 2 Filed 'Dec. 14. 1948 :EII 3 E INVENTOR. PERCY 62 y Oct. 20,1953 RGR ADJUSTABLE SCAFFOLD CLAMP 5 Sheets-Sheet 3 Filed Dec. 14. 19 48 I INVENTOR.

P526) 62 y W.

Patented Oct. 20, 1953 ADJUSTABLE SCAFFOLD CLAMP Percy Gray, Richmond, Calif., assignor of onehalf to William Gray, Washington, D. 0.

Application December 14, 1948, Serial No. 65,231

4 Claims. 1

This invention relates to stages or scaffolds of the type used by painters, decorators and others for providing working access to the various areas of vertical Walls, ceilings, etc. These platforms must be of rugged construction to safely support one ormore workmen. At the same time they must be light in weight since they are frequently shifted from one job to another. These requirements dictate the use of structural materials that provide both lightness and rigidity.

scaffolds of the-typeherein referred to ordinarily comprise a pair of uprights spaced apart and joined by one or more horizontal platforms from which artisans can have unrestricted access to those portions of the vertical wall or overhead ceiling contiguous thereto. The uprights frequently take the form of a pair of step ladders or the equivalent with boards laid horizontally between the rungs thereof. Reliance is placed on. the questionable rigidity of such step ladders in such arrangements since the records of mishaps involving scaffolds show that a step ladder so used is highly unstable and the frequent cause of accidents. used and will probably be continued in use due to their ready availability since the nature of the work' nearly always calls for a ladder in some form and since the material for the improvised platform is always at hand. In addition to planks of the dimensions of floor joists, for example, the horizontal platform is frequently made of interleaved planks so arranged as to constitute an extensible assembly that is strong but light in weight.

. The use of step ladders as above described is due therefore to the fact that they are self-supporting in an erected position as well as bein ordinarily on hand. Although extension ladders,

particularly those in which the side rails diverge at the base are as readily available, are structurally much stronger, and are almost as often needed on the job, little attempt has been made to utilize them in staging due to the difficulty of rigidly uniting the horizontal platform and the vertical ladders. Accordingly as a matter of practice either special scaffold equipment in addition to the usual ladders carried to a job must be provided or a make-shift arrangement of step ladders and horizontal planks must be put together on the job site with consequent risk of accidents as well as obvious inflexibility and difficulty of adjustment of the component parts.

Therefore, it is an object of this invention to provide an improved scaffold clamp by means of which a pair of ordinary ladders and the usual Step ladders are so 2 2 horizontal platform may be transformed into a sturdy, easily adjustable and light weight scuffold.

It is another object of the invention to provide an improved scaffold clamp which enables the weight of the horizontal platform to be carried equitably by a pair of rungs of each ladder.

It is another object of this invention to provide an improved scaffold clamp that is readily adjustable'to not only different heights but also to horizontal platforms of different widths.

It is another object of the invention to provide an improved scaffold clamp that not only distributes the weight of the horizontal platform on two or more rungs of each supporting ladder but is adjustable to compensate for the variable spacing between such rungs. l

It is another object of the invention to provide an improved scaffold clamp in which the horizontal platform is securely and safely locked against inadvertent dislodgement and separation of the ladder rungs therefrom when in use.

A further object of the invention is to provide an improved scaffold clamp by means of which a horizontal platform may be rigidly united to a pair of ordinary ladders of various widths to form a source and safe working scaffold.

A still further object is to provide a readily 1 adjustable and sturdy scaffold which is largely made of components already in use by journeyman artisans and which therefore may be assembled and utilized at an extremely low cost.

The invention possesses other objects and features of advantage, some of which, with the foregoing, Will be set forth in the following description of the preferred form of the invention which is illustrated in the drawing accompanying and forming part of the specification. It is to be understood, however, that variations in the showing made by the said drawing and description may be adopted within the scope of the invention as set forth in the claims.

Reference is now made to the drawings where- Figure 1 is a perspective'view of one form of my improved clamp in use with a pair of ladders and horizontal platform and forming a rigid working scaffold,

Figure 2 is a plan view of the lower one of my scaffold clamps with portions of the platform and the opposite ladder omitted for the sake of clearness,-

Figure 3 is an end elevation of the lower scaffold clamp of Figure 1 taken from the left end on an enlarged scale and taken from the rear of such view,

Figure '7 is a perspective view similar to Fi ure 6 but showing the vertical adjustment provided by my improved scaffold clamp, and Figure 8 is a vertical sectional view taken on the line 88 of Figure 7.

Figure 9 is a perspective view of a modified form of clamp, showing the same attached to a platform. Figure 10 is a view similar to Figure 9 but with the clamp in inoperative position and the platform removed. Figure 11 is a side view of the clamp showing the clamp of Figures 9 and 10 operatively attached to the platform and ladder.

Referring now to the first embodiment Of my invention and more particularly to Figures 1 to 3 of the drawing, it will be observed that a pair of vertical ladders indicated generally by the reference numerals I and 2 and each of which is composed of a pair of vertically extending rails 3 and 4 separated by a plurality of horizontal rungs 5 are spaced apart by the usual distance of a horizontal stage or platform generally indicated at 6. Although ladders of the diverging base type ar preferred because of their easy availability, I have shown, to emphasize the lateral stability inherent therein, diverging base extensions 1 and 8 bolted or otherwise securely attached to the lower ends of the parallelly extending vertical rails 3 and 4.

The scaffold clamp of this invention indicated enerally at 9 in Figurel is constituted of a pair ofnsimilarly shaped members, each of which has thefunction of encasing the end portions of onehalf of the horizontal platform 6 and distributing the weight thereof upon a pair of the adjacent horizontal and parallel rungs 5. Each such member, therefore, comprises in effect a channel formed preferably of a single piece of sheet metal bent to provide a top, triangular portion [0, an outside rectangular portion II, a similar, bottom triangular portion l2, and an endrectangular portion l3. The inwardly extending apex portions of the upper and lower triangles of the members 9 overlap so that they may be united as by a bolt [4 and wing nut I5, the former passing through aligned apertures in the four triangles as shown in Figure 3. One pair of such triangular portions is bent upwardly as shown in Figure 3 to provide a vertically offset portion so that the major portions of the triangles lie in the same plane closely fitting the upper and lower surfaces of the planks comprising the platform. If desired, means may be provided .on the end rectangular portions i3 of the oppositely disposed clamp members to enable them to be easily drawn together to insure registry of the apertures of the triangular'portions referred to. Such means may comprise a pair of horizontally disposed and vertically spaced ears [3a projecting outwardly from one of the end portions l3 and a bolt I3b' pivotally connected to the other end member and disposable between said ears I30. in which it may be retained and effectively shortened through rotation of a wing nut I 30 threaded thereon.

Platform 6 is comprised of a series of spaced planks I6 of preferably rectangular cross section held in spaced relation by a transverse bridge piece l1 and inter-leaved with a similar series of planks I8 united by a bridge member [9. The end portions of the planks are maintained in spaced disposed alternately thereof relation by spacer blocks 20 as is clearly shown in Figure 1. It will be understood that the two series of planks constitute an extensible assembly that may be lengthened or shortened without in any way disturbing the scaffold clamps or their connection to the ladders I, 2 now to be described; such adjustment merely varies the extent of the central overlap of the planks.

For supporting the platform carrying portions of clamp 9 there is united to each end rectangular portion IS, a vertically extending hanger 2| formed preferably of steel strap and provided with a U-shaped hook portion 22 at its upper end adapted to fit over the upper rung nearest the-platform 6 and a similarly shaped lower hook 23 adapted to partially encircle the next lower rung. To provide vertical adjustability between hook portions 22 and -23 I prefer to make the lower hook 23 of a. short length of steel strap and disposed beneath the upper hook 22 in rung engaging position so that its rear fiat side rests against the hanger 2!. The latter is suitably apertured for receiving suitable connecting means such as bolt 24 passing also through a vertical slot in the flat side of book 23 and permitting relative vertical adjustment between the hooks. A brace member is indicated at 25 having its ends bent over into parallelism with the bottom triangular portion l2 and the lower portion of the hanger 2|, respectively, is securely united to these portions as by welding and provides thereby a strong, right triangular structureZ Uniting of end rectangular portion 'l3to "the hanger 2| is also preferably' ac'complished by welding; although it will be obvious that other fastening means such as rivets could also be used:

From the foregoing it will be observed that there has been described a clamp-which rigidly unites a horizontal platform or stage to apair of spaced, vertical ladders of unusual design. Such clamp is readily detachable when it is de{ sired to raise or lower the platformand requires merely the application'of a lifting force to the clamp sufiicient to enable the hook portions of the hanger to be clear of the rungs. Inthe event that an additional safeguard is desired to make impossible the inadvertent lifting offthe hanger from the rungs, a bolt as 26 may be passed through aligned apertures in the parallel legs of the hook portions as is shown at the upper end of ladder l in Figure 1. This figure also shows the use of a hanger 21 having engagement .with but one rather than two rungs of ladder ,l in arrangements where the scaffold rigidity .is ,provided by the lower clamp and attached platform already described. Coupling collars 28 formed of sheet metal, for example, and encircling the abutting ends of ladder l and its upward extension la may be'used to uniteas many ladder sections as desired provided a suificient number of clamps 9 are provided in the assembly as described. Also the clamp of this invention al.- though as described is of fixed lateral extent and hence most perfectly adapted to receive a horizontal platform of the width shown in thedrawing, it is nevertheless capable of accommodating platforms of lesser width by theinsertion of outside spacer blocks 20 of such width as to insure a snug engagement of the platform :ends Within such clamp. Since the clamp extends for a con- .siderable distance in the longitudinal extent of the platform, great rigidity in the united plat form ends, clamp and vertical ladders is thereby assured.

In Figures 4 to 8 of the drawing there is shown a 'more advanced embodiment of my invention. incorporating' automatic locking means for the hook portions of the hanger and the rungs and also a more easily operated. adjustment for the vertically spaced hooks. Considering first the locking means referred to, attention is directed to Figures 4; 5 and 6' which show at the upper end of the hanger 2|, a generally rectangular slot elongated in a vertical direction and disposed opposite the hook portion 22' of the hanger 2|. Pivotally mounted on the opposite face of hanger 2| is a locking dog or latch 3| havin a short arm 32 which is adapted to move into and out of the slot 3|). It will be noted that arm 32 is provided with an upper surface 33 which inclines downwardly when the arm is in its innermost position within the slot 35. The effect of such inclination is to more securely maintain the ladder rung in its locked position therein since an inadvertent upwardly exerted force against the platform and clamp will result in a camlike looking movement of arm 32 in a downward direction to block to a greater extent than before the open portion of the book 22. The locking action of arm 32 just described is efiectuated through the provision of an integral stop arm 34 diverging away from arm 32 in an outward direction serving both as a stop when in engagement with the portion of hanger 2| 10- cated just above slot 3!! and also as means for moving the arm 32 outwardly when it is desired to lift the hanger hook 22 from the ladder rung 5 as when changing the elevation thereof or disassembling the scaffold.

As an integral mounting for the arms 32 and 32 I prefer to provide a vertically disposed, central arm 35 pivoted on a stub shaft 33 extending horizontally and journ-aled in a pair of pedestal blocks 3? and 33 which are mounted in spaced relation on the inner face of the hanger 2|. Pedestal blocks 3? and 33 can be suitably welded to hanger 2|. However, it is preferred to provide the angularly disposed base portions thereon attached to hanger 2| as by means of screws 4| passing therethrough.

To insure that arm 32 is always 'inits inner position extending across the open end of the hook 2-2 in such manner as to look the contained rung therein; suitable spring biasing means is provided. Such means is shown as comprising a flat spring 42 attached to hanger 2| as by a screw 43 and having an outwardly offset portion 44 extending centrally upward between the hanger 2| and the central arm 35 and pressing against the ladder to urge the arm 32 into the slot 30. It will be noted that central arm 35' is cut away from a point opposite the lower edge of slot: 36 to a point below the horizontal plane containing the stub shaft 33 to provide a shoulder 45' against which the upper end of spring end 44 presses, the pedestal blocks 37 and 38 being of such horizontal height as to provide for a free movement of arm 32 into and out of slot 36.

In addition to the foregoing advantages of the automatic locking means shown in Figures 4, 5 and 6, it is desired to mention also the function of the lower curved wall of the arm 32 in facilitating passage of the rung 5 thereacross and into its seated position in the hook 22 as Well as the outer curvature at 22a of the terminal hook portion to allow the latter to more easily slip over the rung when moving the clamp assembly into its desired position. These features are of con-- siderable value in the use of the invention in connection with rungs that are slightly oversize or bowed.

Figures 4,. 5, 7 and 8 of the drawing also disclose an improved form of adjustin means for the hook portion of the hanger 2| whereby the lower hook 23 may be readily adjusted to compensate for the slight variation in spacing of the ladder rungs that is frequently encountered. As shown more particularly in Figures 7 and 8, instead of aperturing the hanger 2| and hook 23 for the reception of a bolt 24 as in the form of the invention first described, there is provided in the lower portion of hanger 2| a vertically elongated slot 48, rectangular in outline. Slidably' confined within such slot 43 is guided a spacer block 49 which is made integral with hook 23 as by welding. Spacer block also carries on its outer face a retainer block 53 of greater width than block 49 to which it is secured as by screws 5| extendingthereinto. In spaced relation above the slot 48 there is provided a threaded bolt 52 extending through the hanger 2| and suitably affixed thereto and with its threaded portion ex tending outwardly to receive an eccentrically apertured, shouldered washer 53. The latter is formed integral with or suitably united to a wing nut 54' which is centrally apertured and threaded to engage the threaded portion of bolt 52. Accordingly as the wing nut 34 is I rotated the shouldered washer 53 will also rotate and will move the retainer block 53 vertically in the slot 38 and thus vary the longitudinal relationship between hanger 2| and hook 23, consequently varying the spacing between the hooks 22 and 23. It will be appreciated that this movement is relatively slight and is sufficient only to compensate for slight irregularities in spacing of the rungs 5 which isfound in many newly manufactured ladders as well as those which have been in use for some time. In practice I have found that such irregular spacing ordinarily does not exceed inch. However, for the clamp to equally distribute the weight of the platform 6 on the two adjacent rungs such adjustment is quite important since it affects the rigidity andhence the safety of the assembled unit when in use.

In Figures 9 to 11 inclusive, I have also shown the clamp of a modified construction. In this embodiment, there are provided clamping portions .56 and 51 arranged to engage respectively over and under the top and bottom surfaces of the platform at the end thereof and being connected together preferably by hinges 53 which are positioned to overlie the end face of the platform when the clamp is operatively mounted on the platform. As here shown the lower clamping portion 5? is formed with angular extensions 59 which merge with the hinge structure and are designed to abut the end face of the platform. The portions 5 5 and E? are moved into tight engagement with the platform by means of a wedge 66 which depend from the upper portion 53 and is arranged to enter one of the spaces between the plank sections it and I8 and forc ibly engage one of the spacer'blocks 23 so the latter will be tightly confined between the wedge and the extensions 59. To secure the clamp in position, a bolt 3| is passed through aligned holes 62 and. 53 adjacent the free ends of the clamp portions and through one of the spaces between the sections aforesaid in the platform,

the bolt 61 being retained in position by means of a wing nut 66 engaging on the threaded shank of the bolt. The hanger members 6?! for mounting the clamp on the ladder are preferably welded or otherwise fixed to the extensions 59, and such hangers are each formed with the hooks 68 and 69 for engagement over the ladder rungs. A brace H is interposed between the lower end of the hanger members and the free end portions of the lower clamp plate 51. As will be understood, the clamp may be disengaged from the platform by merely removing bolt 6|, or it may be quickly remounted on the platform by simply holding the free ends of the clamp portions apart so as to receive the end of the platform, and then replacing and tightening the bolt. If desired means may be provided for holding the plates against sidewise displacement on the end face of the platform. As here shown such means are in the form of lugs 72 projecting from the inner edge of the angular extensions 59 and arranged to seat in suitable recesses in the platform.

From the foregoing, it will be apparent that there has been described a plurality of forms of a simple, inexpensive, highly adaptable and efiicient clamp which may be utilized for transforming readily available ladders and platform into a safe and strong scaffold having a wide application in many fields. It will also be under stood that while it is preferable to utilize the clamps of my invention at both ends of a platform, a clamp may be utilized at only one end, and some other arrangement provided for supporting the platform at the other end.

I claim:

1. Apparatus for securing a vertical ladder and a horizontal platform into a rigid, readily adjustable scaffold unit comprising a pair of united members of oppositely facing U-configuration for receiving the end portions of the platform therebetween in firm engagement, each of said members also including an integral, vertically extending hanger having a pair of vertically spaced hook portions for seating over the adjacent rungs of said vertical ladder, one of said hook portions being provided with means for locking its supporting rung therein and the other of said hook portions including means whereby it may be relatively adjustable with respect to the other hook portion for compensating for varia- U tions in the spacing of said ladder rungs, said other of said hook portions being vertically movable relative to said hanger, and said adjustable means including a cam-like rotary element rotatably mounted on said hanger and engageable with a portion of said other hook portion for limiting vertical movement of the latter.

2. Mechanism for converting a pair of vertical ladders and a horizontal platform into a rigid, readily adjustable scaffold comprising a pair of centrally united members of oppositely facing U- configuration for receiving the end portions of the platform therebetween in secure engagement, each of said united members also including an integral, vertically extending hanger having a pair of vertically spaced hook portions for seating over the adjacent rungs of said vertical ladder, one of said hook portions being slotted, a locking arm pivotally mounted on said hanger and movable into locking engagement through said slot beneath said supporting rung and outwardly from said slot into a released position, and spring means normally urging said arm into said locking engagement.

3. A device for converting a pair of vertical ladders and a horizontal platform into a rigid, readily adjustable scaffold comprising a pair of centrally united members of oppositely facing U-configuration for receiving the end portions of the platform therebetween in secure engagement, each of said united members also including an integral, vertically extending hanger having a pair of vertically spaced hook portions for seating over the adjacent rungs of said vertical ladder, one of said hook portions being vertically adjustable with respect to the other hook portion and the latter portion being slotted, a locking arm pivotally mounted on said hanger below said slot and movable into locking engagement through said slot beneath said supporting rung and outwardly from said slot into a released position, said arm including a stop member disposed outwardly of said hook portion and limiting the movement of said locking arm in one direction, and means normally urging said arm in said one direction.

4. Apparatus for converting a pair of vertical ladders and a horizontal platform .into a rigid, readily adjustable scaffold comprising a pair of centrally united members of oppositely facing U- configuration for receiving the end portions of the platform therebetween in secure engagement, each of said united members also including an integral, vertically extending hanger having a pair of vertically spaced hook portions for seating over the adjacent rungs of said vertical ladder, said hanger including a longitudinally extending slot, a spacer block integral with one of said hook portions and slidable in said slot, 2. retainer block carried by said spacer block and a manually operated eccentrically shouldered n-ut carried by said hanger and rotatable to effect relative movement between one of said hook portions and said hanger whereby the spacing between said hook portions may be varied to compensate for variations in spacing of said ladder rungs.

PERCY GRAY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 350,153 Petty Oct. 5, 1886 362,747 Higgins May 10, 1887 567,755 Stillman Sept. 15, 1896 711,384 Carman 'Oct. 14, 1902 1,129,218 Macklem Feb. 23, 1915 1,179,166 Crist et a1 Apr. 11, 1916 1,359,452 Walker Nov. 16, 1920 1,376,924 Dixson May 3, 1921 1,672,502 Roth June 5, 1928 1,825,590 Hollister Sept. 29, 1931 2,136,420 Edwards Nov. 15, 1938 2,430,642 Mahaifey Nov. 11, 1947 2,439,185 Patt Apr. 6, 1948 FOREIGN PATENTS Number Country Date 208,353 Germany Mar. 23, 1909 

